Pit-1 (POU1F1) is a POU-homeodomain transcription factor, and it is one of the most important tissue-specific transcription factors in pituitary development. Cyclin-dependent kinase 5 (CDK5) is a protein kinase that can phosphorylate many key transcription factors, but the mechanism under which CDK5 phosphorylates Pit-1 is unclear. To investigate whether CDK5 can regulate cell proliferation and promote hormone secretion through phosphorylation of Ser126-Pit-1 in prolactinomas, we generated an antibody that specifically recognizes phosphorylated serine at position 126 of Pit-1 (Ser126-Pit-1). We used western blotting to detect the level of Pit-1 phosphorylation and observed the proliferation and apoptosis of GH3 cells with different levels of Pit-1 phosphorylation by clone formation experiments, cell viability assays, and flow cytometry. ELISA was used to measure the level of PRL in the supernatant of GH3 cells. Tissue microarrays and immunohistochemistry were used to evaluate the expression of the phosphorylation level of Ser126-Pit-1 (pSer126-Pit-1) in prolactinomas. Our data indicated that Ser126-Pit-1 is specifically phosphorylated by CDK5 and high-level pSer-126-Pit-1 can promote cell proliferation and PRL secretion. In addition, a higher level of pSer-126-Pit-1 correlates with a worse prognosis in patients with prolactinoma. Our results show that CDK5 mediated Ser126-Pit-1 phosphorylation and regulated prolactinoma progression and PRL secretion.

中文翻译：

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细胞周期蛋白依赖性激酶 5 在丝氨酸 126 处磷酸化 Pit-1 与催乳素瘤的细胞增殖和不良预后有关

Pit-1 (POU1F1) 是一种 POU 同源域转录因子，是垂体发育中最重要的组织特异性转录因子之一。细胞周期蛋白依赖性激酶 5 (CDK5) 是一种可以磷酸化许多关键转录因子的蛋白激酶，但 CDK5 磷酸化 Pit-1 的机制尚不清楚。为了研究 CDK5 是否可以通过磷酸化催乳素瘤中的 Ser126-Pit-1 来调节细胞增殖和促进激素分泌，我们生成了一种抗体，该抗体可特异性识别 Pit-1 的 126 位磷酸化丝氨酸 (Ser126-Pit-1)。我们使用蛋白质印迹法检测Pit-1磷酸化水平，并通过克隆形成实验、细胞活力测定和流式细胞术观察具有不同Pit-1磷酸化水平的GH3细胞的增殖和凋亡。ELISA用于测量GH3细胞上清液中PRL的水平。组织微阵列和免疫组织化学用于评估催乳素瘤中 Ser126-Pit-1 (pSer126-Pit-1) 磷酸化水平的表达。我们的数据表明，Ser126-Pit-1 被 CDK5 特异性磷酸化，高水平的 pSer-126-Pit-1 可以促进细胞增殖和 PRL 分泌。此外，较高水平的 pSer-126-Pit-1 与催乳素瘤患者的预后较差相关。我们的结果表明 CDK5 介导 Ser126-Pit-1 磷酸化并调节催乳素瘤进展和 PRL 分泌。我们的数据表明，Ser126-Pit-1 被 CDK5 特异性磷酸化，高水平的 pSer-126-Pit-1 可以促进细胞增殖和 PRL 分泌。此外，较高水平的 pSer-126-Pit-1 与催乳素瘤患者的预后较差相关。我们的结果表明 CDK5 介导 Ser126-Pit-1 磷酸化并调节催乳素瘤进展和 PRL 分泌。我们的数据表明，Ser126-Pit-1 被 CDK5 特异性磷酸化，高水平的 pSer-126-Pit-1 可以促进细胞增殖和 PRL 分泌。此外，较高水平的 pSer-126-Pit-1 与催乳素瘤患者的预后较差相关。我们的结果表明 CDK5 介导 Ser126-Pit-1 磷酸化并调节催乳素瘤进展和 PRL 分泌。